Piling methods

ABSTRACT

A method of casting a concrete pile in situ using a former which is extracted following the casting of the pile, the former, with a concrete plug cast in its lower end and while the plug is in a semi-hardened state being driven into the site by the action of a driving monkey on the plug and then the combination of a counterweight (driving monkey) rested on the plug and a vibrator extractor on the former used to free any bond between the plug and former and withdraw the former part-way up the plug whereupon the counterweight is removed and reinforcing and cementious mixture is placed in the former to form the pile and the former is then extracted using the vibrator at a rate commensurate to the hardening rate of the cementious mixture.

ilrtite States Patent 11 1 Gilberd' [4 Oct. 22, 1974 PllLlNG METHODS Gordon Henry Gilberd, Auckland, New Zealand Gilberd Hadfield Pile Company, Limited, Mt. Roskill, Auckland, New Zealand Filed: Oct. 15, 1973 Appl. No.: 406,359

inventor:

Assignee:

Foreign Application Priority Data Oct. 20, 1972 New Zealand 168757 US. Cl til/53.6, 61/5362, 61/5364 Int. Cl E02d 5/44 Field of Search 61/5364, 53.66, 53.6,

References Cited UNITED STATES PATENTS 6/l930 Frankignoul 61/5364 l2/l939 Cleesattel 61/5364 X 3,568,452 3/197] Stifler, Jr. (ii/53.6

Primary Examiner-Jacob Shapiro Attorney, Agent, or Firm-Limbach, Limbaeh &

Sutton ABSTRACT the former part-way up the plug whereupon the counterweight is removed and reinforcing and cementious mixture is placed in the former to form the pile and the former is then extracted using the vibrator at a rate commensurate to the hardening rate of the cementious mixture.

4 Claims, 4 Drawing Figures PILING METHODS This invention relates to a method of casting concrete piles in situ.

BACKGROUND OF THE INVENTION The intention of this invention is to provide a cast, in situ, concrete piling method enabling a former for the cast pile to be extracted following the casting operation.

SUMMARY OF THE INVENTION According to one aspect of this invention there is provided a cast, in situ, concrete piling method comprising the steps of casting a concrete plug in an end of a former and while the plug is in a semi-hardened state driving the former with the plug lowermost into a site by the use of a driving monkey acting on the plug, providing a counterweight on the plug, mounting a vibrator extractor on the former and operating the extractor at a frequency that will free any bond between the former and plug and then withdrawing the former partway up the plug, removing the counterweight, inserting reinforcing and cementious mixture into the former to form a pile and using a vibrator extractor to extract the former at a rate commensurate to the hardening rate of the cementious mixture.

BRIEF DESCRIPTION OF THE DRAWINGS DETAILED DESCRIPTION OF CERTAIN PREFERRED EMBODIMENTS Referring now more particularly to FIG. 1, a cylindrical steel tube is utilized as a former 1 to cast a pile in situ. A concrete plug 3 is cast in an end of former l. Preferably plug 3 extends longitudinally of former l a distance approximately two and a half times the diameter of former 1. With this arrangement it is found that the adhesive bond inherent in plug 3 while in a semihardened state combined with a'frictional bond, mentioned in more detail hereinafter, between former l and plug 3 will withstand the following described driving operation.

Former 1, with plug 3 lowermost, is then driven into the required site (ground level being indicated by Line to the necessary founding depth. A driving monkey 6 preferably of a diameter equal to at least half the diameter of former l, is utilized in conventional manner within former l to act on plug 3 in this driving operation.

It is found that the frictional bond, mentioned'aforesaid created by the action of monkey 6 on plug 3 in its semi-hardened state tends to compressively distort plug 3 creating a radially directed component of the driving action bearing against former 1 resulting in a frictional bond being created therebetween which in combination with the adhesive bondis sufficient to cause foring characteristics of the cementious mixture utilized in plug 3, the type of site involved and the particle size of the constituents of the mixture of plug 3.

Noramlly this operation can be commenced within a matter of hours of casting plug 3 within former 1. At the other end of the possible range plug 3 may be cast in former 1 and by keeping plug 3 dampened com- 'mencement of this operation may be delayed, for example, overnight.

On completion of the driving operation a counterweight preferably driving monkey 6 is then rested on plug 3.

Referring to FIGS. 2 and 3, a vibratory extractor 9 is then clamped in conventional manner to the head of former 1. By adjusting the frequency of the vibrator extractor 9 it is found that any remaining adhesive bond between plug 3 and former 1 is freed. The positioning of the counterweight. upon plug 3 during the vibrating action appears to nullify the vibrating action upon plug 3 as a whole which remains substantially uneffected in its position in the site, the vibrating action tending to free the peripheralsection of plug 3 outside its central portion under the compression influence of monkey 6 resting thereon.

During this step and maybe overlapping with the next step a pre-mixed cementious grout 7 is preferably placed on top of plug 3. Experiments indicate that grout 7 assists, by lubricating, the freeing of any bond between plug 3 and former 1 and the subsequent withdrawal of former 1, described hereinafter. The cementious grout 7 hasan additional function also mentioned hereinafter. a In the preferred form the vibrator extractor 9 is adjusted to operate at approximately 1,250 oscillations per minute, it being found that at this frequency, maybe in combination with the addition of cementious grout 7, the freeing of the bond between plug 3 is obtained within a short interval of time.

Following the freeing of any bondthe vibratory extractor 9 is used in conventional manner to withdraw former l part-way up plug 3, preferably an amount equal to twice the diameter of former 1. Plug 3 remains substantially at its grounding level and the cementious grout 7 penetrates about the periphery of plug 3 and will enter any annular space 8 which may be formed, particularly in harder ground, by the withdrawn of former l.

Referring to FIG. 4, further cementious mixture,

preferably tending to be dry, may at this stage be placed on'plug 3 and driving monkey 6 then used to force that cementious mixture about the periphery of plug 3 tojform a bulb base 10, the necessity or otherwise of this step of the operation being basicly dependant upon the type of sub-strata of the site.

Driving monkey 6 is then withdrawn and the required reinforcing 11 and cementious mixture 12, which is preferably of high workability, for a pile is placed within former l. The vibrator extractor 9 is then used to slowly extract former 1 from the site. A vibratory type extractor is preferably used as its vibrations facilitate compaction-of cementious mixture 12. The timing of this extraction process is related to the hardening rate of cementious mixture 12 which in the form of the required pile takes-up the shaft left by extraction of former l.

By such method it will be appreciated that the possibility of loose or unstable material adjacent the shaft intruding thereinto is alleviated.

Thus by this invention there is provided a method of casting a pile in situ which enables a former for the pile to be removed and may be utilized in another piling operation.

The terms and expressions which have been employed here are used as terms of description and not of limitation, and there is no intention, in the use of such terms and expressions, of excluding equivalents of the features shown and described, or portions thereof, it being recognized that various modifications are possible within the scope of the invention claimed.

What is claimed is:

l. A method of casting a pile in situ comprising the steps of casting a concrete plug in an end of a former and while the plug is in a semi-hardened state, driving the former with the plug lowermost into a site by the use of a driving monkey acting on the plug, providing a counterweight on the plug, mounting a vibrator extractor on the former, and operating the extractor at a frequency that will free any bond between the former and plug and thenwithdrawing the former part-way up theplug, removing the counterweight, inserting reinforcing cementious mixture into theformer to form a pile and using a vibrator extractor to extract the former at a rate commensurate to the hardening rate of the cementious mixture.

2. A method of casting a pile in situ as claimed in claim 1 further comprising the step of inserting a cementious grout during the process of operating the extractor to free any bond between the former and the plug.

3. A method of casting a pile in situ as claimed in claim 1 wherein the driving monkey is utilized as the counterweight and wherein the vibrator extractor used in freeing the bond between the plug and former is also used in extracting the former from the site.

4. A method of casting a pile in situ as claimed in claim 1 including the step of applying a cementious mixture to the top of the plug following the part-way withdrawal of the former from the plug and thenusing a driving monkey to force the cementious mixture past thelperiphery of the plug to form a bulbed base. 

1. A method of casting a pile in situ comprising the steps of casting a concrete plug in an end of a former and while the plug is in a semi-hardened state, driving the former with the plug lowermost into a site by the use of a driving monkey acting on the plug, providing a counterweight on the plug, mounting a vibrator extractor on the former, and operating the extractor at a frequency that will free any bond between the former and plug and then withdrawing the former part-way up the plug, removing the counterweight, inserting reinforcing cementious mixture into the former to form a pile and using a vibrator extractor to extract the former at a rate commensurate to the hardening rate of the cementious mixture.
 2. A method of casting a pile in situ as claimed in claim 1 further comprising the step of inserting a cementious grout during the process of operating the extractor to free any bond between the former and the plug.
 3. A method of casting a pile in situ as claimed in claim 1 wherein the driving monkey is utilized as the counterweight and wherein the vibrator extractor used in freeing the bond between the plug and former is also used in extracting the former from the site.
 4. A method of casting a pile in situ as claimed in claim 1 including the step of applying a cementious mixture to the top of the plug following the part-way withdrawal of the former from the plug and then using a driving monkey to force the cementious mixture past the periphery of the plug to form a bulbed base. 